1. Field of the Invention
The present invention relates to a curing machine for pneumatic tires wherein the exchange of the bladders can be performed highly efficiently, in a simplified manner and within a minimized time.
2. Description of Related Art
As generally known in the art, curing machine for pneumatic tires includes a bladder for heating and pressurizing a green tire from its inner side, to thereby perform curing of the green tire and obtain a product tire. The bladder is detachably held by upper and lower bladder rings of the curing machine in air tight manner. To this end, it has been a conventional practice that a pair of upper bladder rings are connected to each other by screws so as to clamp the upper surface of the bladder therebetween, and a pair of lower bladder rings are similarly connected to each other by screws so as to clamp the lower surface of the bladder therebetween, thereby forming a bladder assembly. The curing machine further includes a vertically movable center post for holding the upper bladder rings, which is provided with a threaded top end portion and a flange-like collar on the lower side of the top end portion. An outer cylinder is arranged on the radially outer side of the center post, for supplying a pressurized heat medium into an interior of the green tire. The outer cylinder is also provided with a threaded top end portion. The upper bladder ring has a center through hole through which the threaded top end portion of the center post can be passed. The lower bladder ring has a threaded center hole which can be fastened to the threaded top end portion of the outer cylinder.
In order to mount a bladder onto the curing machine, the top end portion of the center post is passed through the center through hole of the upper bladder ring so as to suspend the bladder assembly. The threaded center hole of the lower bladder ring is then aligned with the threaded top end portion of the outer cylinder and fastened thereto by rotating the entire bladder assembly about the center axis of the outer cylinder. Subsequently, a nut is fastened to the threaded top portion of the center post to complete the mounting operation of the bladder assembly onto the curing machine.
In order to remove the bladder assembly from the curing machine, the above-mentioned steps are reversed. Thus, the nut is disengaged from the top end portion of the center post, and the bladder assembly as a whole is then rotated about the center axis of the outer cylinder to disengage the lower bladder ring from the outer cylinder, thereby allowing removal of the bladder assembly from the curing machine.
The above-mentioned mounting and removing operations of the bladder assembly to and from the curing machine is troublesome and time consuming, so that it has been difficult to improve the working efficiency and manufacturing productivity. Moreover, it is a general practice that tire factory is in full operation, i.e., 24 hours a day, and a curing machine is used to produce various tires with different specifications, thereby requiring changes to the curing mold and bladder assembly. The curing of tires is performed using high temperature gas, and the curing machine has substantial heat capacity. Thus, the interior of the machine immediately after it has been operated exhibits a high temperature so that the factory workers are exposed to a severe working environment for a long time. It is highly desirable to improve the working environment at tire factories, and it is highly important in this respect to ensure that exchange of the bladders can be performed highly efficiently, in a simplified manner and within a minimized time.
It is therefore a primary object of the present invention to provide an improved curing machine which allows the bladders to be exchanged highly efficiently, in a simplified manner and within a minimized time.
According to a first aspect of the present invention, there is provided a curing machine for pneumatic tires, comprising: a bladder for heating and pressurizing a green tire from its inner side; upper and lower bladder rings for holding a bladder in air-tight manner, said upper bladder ring having upper and lower surfaces and a center through hole; a vertically movable center post for holding said upper bladder ring, said center post having a top end portion which can be passed through said center through hole in the upper bladder ring; and an upper lock mechanism associated with the top end portion of the center post for automatically locking the upper and lower surfaces of the upper bladder ring to the center post after the top end portion of the center post has been passed through the center through hole in the upper bladder ring.
According to a second aspect of the present invention, there is provided a curing machine for pneumatic tires, comprising: a bladder for heating and pressurizing a green tire from its inner side; upper and lower bladder rings for holding a bladder in air-tight manner, a vertically movable center post for holding said upper bladder ring; an outer cylinder arranged on a radially outer side of the center post, for supplying a pressurized heat medium into an interior of the green tire; a lower lock mechanism for locking the lower bladder ring to the outer cylinder, said lower lock mechanism comprising: (i) a lock region extending downwards from the lower bladder ring; (ii) a first lock means secured to an outer side of the outer cylinder; and (iii) a second lock mechanism which can be vertically moved on an outer side of the first lock means so that the first lock means is engaged with the lock region of the lower bladder ring and locked with each other by vertically moving the second lock means in a predetermined direction, and unlocked from each other by vertically moving the second lock means in the opposite direction.
According to a third aspect of the present invention, there is provided a curing machine for pneumatic tires, comprising: a bladder for heating and pressurizing a green tire from its inner side; upper and lower bladder rings for hold a bladder in air-tight manner, said upper bladder ring having a center through hole; a vertically movable center post for holding said upper bladder ring, said center post having a top end portion which can be passed through said center through hole in the upper bladder ring; an outer cylinder arranged on a radially outer side of the center post, for supplying a pressurized heat medium into an interior of the green tire; an upper lock mechanism associated with the top end portion of the center post for automatically locking the upper bladder ring to the center post after the top end portion of the center post has been passed through the center through hole in the upper bladder ring; and a lower lock mechanism for locking the lower bladder ring to the outer cylinder, said lower lock mechanism comprising: (i) a lock region extending downwards from the lower bladder ring; (ii) a first lock means secured to an outer side of the outer cylinder; and (iii) a second lock means which can be vertically moved on an outer side of the first lock means so that the first lock means is engaged with the lock region of the lower bladder ring and locked with each other by vertically moving the second lock means in a predetermined direction, and unlocked from each other by vertically moving the second lock means in opposite direction.